Farnesoid X Receptor (FXR, NR1H4) is a member of the nuclear receptor family of ligand-activated transcription factors that includes receptors for the steroid, retinoid, and thyroid hormones (D. J. Mangelsdorf, et al., Cell, 1995, 83(6), 841-850). FXR was originally identified from a rat liver cDNA library. Farnesol and derivatives, collectively termed farnesoids, activate the rat ortholog at high concentration, but they do not modulate the human or mouse receptors. FXR is primarily expressed in the liver, kidney, and intestine (W. Seol, et al., Mol. Endocrinol., 1995, 9(1), 72-85; B. M. Forman, et al., Cell, 1995, 81(5), 687-693). The relevant physiological ligands of FXR include the primary bile acids cholic acid (CA) and chenodeoxycholic acid (CDCA) and the secondary bile acids deoxycholic acid (DCA) and lithocholic acid (LCA) (D. Parks, et al., Science, 1999, 284(5418), 1362-1365). The most potent physiological ligand for FXR is CDCA, which plays a key role in regulating the expression of several genes that participate in bile acid homeostasis. FXR functions as a heterodimer with the retinoid X receptor (RXR) and binds to response elements in the promoter region of target genes to regulate gene transcription. FXR seems to be also involved in paracrine and endocrine signaling by upregulating the expression of the cytokine Fibroblast Growth Factor (J. Holt, et al., Genes Dev., 2003, 17(13), 1581-1591; T. Inagaki, et al., Cell Metab., 2005, 2(4), 217-225).
Small molecule compounds which act as FXR modulators have been disclosed in the following publications: WO 2000/037077, WO 2002/072598, WO 2003/015771, WO 2003/099821, WO 2004/00752, WO 2004/048349, WO 2005/009387, WO 2005/082925, US 2005/0054634, WO 2007/052843, WO 2007/070796, WO 2007/076260, WO 2007/092751, WO 2007/095174, WO 2007/140174, WO 2007/140183, US 2007/0142340, WO 2008/000643, WO 2008/002573, WO 2008/025539, WO 2008/025540, WO 2008/051942, WO 2008/073825, WO 2008/157270, US 2008/0299118, US 2008/0300235, WO 2009/005998, WO 2009/012125, WO 2009/027264, WO 2009/062874, WO 2009/127321, WO 2009/149795, US 2009/0131409, US 2009/0137554, US 2009/0163474, US 2009/0163552, US 2009/0215748, WO 2010/043513, WO 2011/020615, WO 2011/117163, WO 2012/087519, WO 2012/087520, WO 2012/087521, WO 2013/007387, WO 2013/037482, WO 2013/166176, WO 2013/192097, WO 2014/184271, US 2014/0186438, US 2014/0187633, and WO 2015/017813. Further small molecule FXR modulators have been recently reviewed (R. C. Buijsman, et al., Curr. Med. Chem. 2005, 12(9), 1017-1075; Crawley, M. L. Expert Opin. Ther. Patents 2010, 20(8), 1047-1057; V. Sepe, et al., Expert Opin. Ther. Patents 2015, 25(8), 885-896; Xu, Y., J. Med. Chem. DOI: 10.1021/acs.jmedchem.5b00342)).
FXR as an attractive drug target for liver diseases such as Primary Billiary Cirrhosis (PBC) or Non-alcoholic Steatohepatitis (NASH) has been confirmed by recent clinical studies using the bile acid analogue Obeticholic Acid (OCA) (S. Mudaliar et al. Gastroenterology, 2013, 145, 574-582). OCA, however, has a potential to induce cholesterol-related side effects upon prolonged treatment and also shows bile acid like pharmacokinetics. Great efforts have been focused on finding synthetic non-steroidal FXR agonists with general drug likeness and improved pharmacokinetis (C. Kremoser et al., Curr. Med. Chem. 2014, 14, 2143-2158).